Population dynamics of Mythimna separata and its parasitoid, Cotesia ruficrus, on maize in New Zealand

Abstract

Field populations of Mythimna separata and its parasitoid, Cotesia rujicrus, were sampled from maize over two successive seasons. Populations of M. separata larvae (up to 1.5 larvae per plant) were detected in February of both years. Larvae were heavily parasitised by C. ruficrus, which caused mortality of up to 98070. C. ruficrus cocoon masses were hyperparasitised by Eupteromalus spp. from March onwards, but this occurred too late to affect primary parasitism of M. separata. Early collection of C. ruficrus adults adjacent to the crop suggested parasitism of host generations preceding that on the maize. M. separata larvae occurred mostly on mature cobs and did not affect fertilisation or cause significant seed damage.

Keywords:

• Mythimna separata
• Cotesia ruficrus
• Eupteromalus spp
• parasitism
• population dynamics
• hyperparasitism
• maize